1. Field of the Invention
The present invention relates to an exchangeable lens to be used with a lens exchangeable camera, and in particular it pertains an exchangeable lens for use with a camera having a so-called focus aid function of the through-the-lens (TTL) range finding or focus detecting type wherein a focus detecting element receives the light coming from a target object and having passed through the objective lens, and detects the focus condition of the lens, and the focus condition and the direction of defocus are displayed, for example, in the camera viewfinder field to indicate to the user whether the focusing operation should be stopped or continued and in what direction the focusing should be adjusted. The exchangeable lens to which the present invention is applied, includes a zoom lens with the function of macro or close-up focusing.
2. Description of the Prior Art
As the focus aid function is only for indicating the necessity and direction of the focus adjustment in accordance with the focusing condition and direction of defocus detected through the focus detecting element, exchangeable lenses to be used with the same type camera must be designed such that their focus adjusting members are rotated in the same direction for the change of the focused distance in the same direction. If the direction of the rotation of the focus adjusting member is different with the interchangeable lenses, it is likely to occur that the focus aid device indicates for some lenses the direction of focus adjustment which is opposite to the direction in which the focus adjustment must be made. In such a case, if the user adjusts the focusing in accordance with the indication of the focus aid device, the focus adjusting member will be rotated in the direction opposite from the in-focus position and the objective lens will never be focussed.
As to a zoom exchangeable lens which is adjustable for macro or close-up photography as well as for zooming, two types are known. One is a wide-macro type lens which is switched from the zooming to macro focus condition with a part of the lens elements being moved from a wide angle or widest angle condition of the lens system as shown in FIG. 12. The other is a tele-macro type lens wherein a part of the lens elements is moved from the tele or longest focal length condition of the lens system as shown in FIG. 13, in order to switch the lens from the zooming to the macro focus condition. In the wide-macro type lens as shown in FIG. 12, the first, second and fourth lens groups are moved with the third lens group being stationary for the zooming and the first lens group is moved independently for the focusing in normal range. The lens system is switched to the macro focus condition when the second and fourth lens groups are moved by the same amount with the first and third lens groups being left at their widest angle position. As the second and fourth lens groups are moved forward, the lens system will be focused at a nearer distance and the magnification of photography will increase.
In the case of the tele-macro type lens as shown in FIG. 13, the first and second lens groups are moved for the zooming and only the first lens group is moved for the focusing in ordinary range. The lens system is switched to the macro focus condition when the first lens group is moved with the second lens group being left at the longest focal length position. As the first lens group is moved forward, the lens system will be focused at a nearer distance and the magnification of photography will increase.
It is natural for those two types of zoom exchangeable lenses to be designed such that their zooming operation rings are to be rotated in the same direction for the adjustment of focal length from a tele to wide angle condition as well as that their focusing rings or focus adjusting rings are moved in the same direction for the adjustment of focus, in so far as those exchangeable lenses are adapted for use with the same type of camera. Further, the zooming operation ring is usually operated for the macro focusing in the range and direction of the extension from the zoom operation range. Hence, the zooming operation rings of the wide-macro and tele-macro lenses are to be rotated in the opposite directions for the adjustment of focus or focused distance in the macro focus range. In other words, the relationship between the direction of the focus adjusting operation and the change of the focused distance is opposite in the cases of the tele-macro and wide-macro zoom lenses.
The problem due to the inconsistency between the indication given by the focus aid device in the camera and the direction of rotational operation to be actually made, may be avoided if the above mentioned various exchangeable lenses are designed to have a unified direction of the rotational operation or to have a limited range of focus aid operation so that the indication is made correctly for the actual operation. However, such a particular design restricts the flexibility of lens designing and the exchangeable lenses so designed can not be used with cameras of other types or of other camera manufacture. Even in the case of exchangeable lenses to be used with one type of camera, there are limits for the designing of exchangeable lenses with respect to the direction of various operations. For instance, if the direction of zooming operation is unified, then the operational direction for focusing in the macro range can not be unified and vice versa. Hence, problems occur due to the inconsistency between the indication and the direction of operation to be made actually, for the cases beyond the limit.